Integrated circuit devices, such as semiconductor chips, are commonly packaged with a lead frame and an encapsulant structure. In this packaging arrangement, one or more semiconductor chips are mounted to the lead frame and electrically connected to the lead frame. The encapsulant structure covers the lead frame, semiconductor chip and electrical connections. The lead frame includes external electrical terminals that allow the semiconductor chip to be electrically connected to a printed circuit board, for example. Thus, the packaging arrangement provides an electrical connection between the semiconductor chips and other devices while simultaneously protecting the semiconductor chip and electrical connections from damaging environmental conditions, such as moisture, temperature, foreign particles, etc.
Encapsulant structures for semiconductor packages may be formed by different processes. For instance, the encapsulant structure may be formed by a transfer molding process. In a transfer molding process, the encapsulant structure is formed by a liquefied encapsulant material, such as a thermoset resin or an epoxy. According to this procedure, the liquefied encapsulant material is molded in a cavity that surrounds the device and lead frame. The liquefied encapsulant material is then hardened into a solid state and the cavity structure is removed.
One difficulty associated with forming a packaging arrangement using the above described process involves accounting for the flow rate of liquefied molding material. Ideally, the process should be able to uniformly fill different sections of the cavity so that liquefied encapsulant material reaches the end of the cavity sections and ejects trapped air or gas through vents in the cavity. However, this can be difficult or impossible if the liquefied encapsulant material moves at different rates within different sections of the cavity due to non-uniform geometric structures. If the liquefied encapsulant material fills one cavity section before another, flow fronts may merge away from the vents, which may entrap air or gas and cause voiding. Furthermore, unbalanced flow rates of liquefied encapsulant material may result in defective or incomplete encapsulation structures. As a result, the packaging arrangement is less effective or ineffective at protecting the semiconductor chip and electrical connections from damaging environmental conditions, may be more susceptible to delamination, and may have to be discarded.